The South African has shone for club and country since joining Sale at the start of the 2017-18 season.
“It’s humbling to know a club wants to extend your contract, even though you still have more than a year left on your current one!” De Klerk said in a club statement.
“I would not have re-signed if I did not enjoy it here in the north west and really do believe in what we are trying to achieve here at Sale.”
The scrum half scored 97 points in 25 appearances in his first season in England leading to a call up to the Springboks squad for the 2018 summer test series against England in South Africa.
De Klerk put in three exceptional performances in a 2-1 Springbok series win and also played his part in a notable victory over New Zealand in the Rugby Championship.
“I am delighted that Faf has agreed to extend his contract with us,” said Sale director of rugby Steve Diamond.
“Sale Sharks have had some fantastic players throughout the professional era, there are too many to mention, but Faf is one of a few truly world class players who have been at the club.
“His ability, attitude and enthusiasm are second to none and are a testament to professional he is.”